Mechanical Advance

[adumb]

So my sbc 350 has mechanical advance. i had help setting the timing last time. I am looking at buying a PerTronix weight and spring kit. would i set the advance at idle, and then set it holding the trottle at 3k or so? and has anyone used this PerTronix Kit? I am going to be having a 2k stall TC and a 5,800 or 6k redline. I am not sure what springs to look at using. i did the experimenting when installing the gov recal kit, but i am not looking forward to experimenting with this.

 

[82355supreme]

I can't answer the weight question, but have all your timing in by 2,700-3,000 RPMS. No later than 3K for sure. Do you have a dial-back light? If not, either buy one or see if you can borrow one from somebody. This will make the process alot easier (no math :wink: )

If you know exactly how much advance is built into the distributor you can just set the idle timing so that you'll have 36-38* total. Generally there's 20* mechanical advance built in, so you can set idle at 16-18*.

Using a dial back light is the best way though.

 

[dedub]

I bought, built, and run a pertronix flame thrower kit on my 80 ss Elky.
First thing I can say is it's well worth the money. My 1/4 time dropped by .15 sec. That's pretty significant if you think about it. It really woke up the crate 350 I had in it. I used the middle weight spring which puts it at full advance around 3k ish. I found that works fine for me. It also comes with an adjustable vacuum module that you can play with too. A few things I learned during the whole process.
* don't hook your vacuum advance to a ported side of the carburetor. Make sure it's on a full vacuum even at idle.
* as simple as it sounds, set timing with the vacuum advance disconnected. The vacuum advance will add about 16 deg.
* use a sewing tape measure to measure the circumference of your balancer. Mine was 360 cm, divide that number by 10 and that will be the 36 deg mark. So if your circumference was 300 cm then at 30 cm CLOCKWISE from TDC would be your 36 deg mark. Use some chalk or marker or what ever and mark that spot.
Now, REMOVE the springs from the weights, disconnect the vacuum and start the motor and time it. What your seeing is your initial timing which should be around 10 to 12 plus the 20 to 25 of mechanical. 36 is a good base. Now put the springs back on, connect the vacuum which will put it another 16 over the 36 for 52 deg total at high rev and high vacuum.

 

[adumb]

thanks!!!! great response. just curious, your referring to removing the springs on the vacuum and then setting the 10 -12 degrees at idle. then knowing the 20-25 for mechanical and then the 16 for vacuum, correct?

 

[84GP455]

Use the lighter springs and it will open up the weights sooner, the distributor usually comes with the medium springs installed. I changed my springs from medium to light and boy what a difference it made! I have a Pertronix Flamethrower HEI distributor and it comes with an adjustable vacuum advance and it has a total mechanical advance of 23 but the curve is what you adjust to make this 23 degrees come in, which like most people, is all in by 3,000 RPM. by putting the lighter springs in, it will open up sooner on the RPM range. The other guys had a lot of good tips also :wink:

 

[adumb]

i am getting tempted by that dist. but what is it that makes it misfire-free up to 7500? the coil? could i just buy a pertronix coil?

 

[84GP455]

your motor sees 7500 RPM??? that's high revving man!! Yes it could be your coil, you could try and change that first, and it could also be your ignition module, those are 2 important parts in the distributor so while you're at it, you may as well buy a new distributor for $220 and feel better knowing it's all new! then you can set your timing because you will know the mechanical advance for that distributor.

 

[adumb]

your motor sees 7500 RPM??? that's high revving man!! Yes it could be your coil, you could try and change that first, and it could also be your ignition module, those are 2 important parts in the distributor so while you're at it, you may as well buy a new distributor for $220 and feel better knowing it's all new! then you can set your timing because you will know the mechanical advance for that distributor.

no, mine doesn't see 7500. but the dist. is rated up to that. i am thinking about going with the flamethrower. take the guess work out of setting it up.

 

[shotgun]

adumb, Hi-jack alert!!!!!

Could you get me some detail shots of the rear quarter window area.
I parted a non-vinyl car and it would help to see what it "should" like when I convert my Landue car.

Thanks.

 

[adumb]

adumb, Hi-jack alert!!!!!

Could you get me some detail shots of the rear quarter window area.
I parted a non-vinyl car and it would help to see what it "should" like when I convert my Landue car.

Thanks.

sure thing, its raining today, but i'll get some shots tomaro.